This application is based on an application No. 2000-84337 filed in Japan, the content of which is hereby incorporated by reference.
1. Field of the Invention
The present invention relates to a fluorescent lamp and a manufacturing method for the same. More particularly, the invention relates to improvements for enhancing the productivity of a fluorescent lamp which is equipped with a reflector to uniformize light distribution, and techniques for maintaining uniform light distribution of such a fluorescent lamp for a long time.
2. Background Art
In general, when a discharge path of a fluorescent lamp is made serpentine, a long discharge path can be formed in a small space, which enables the fluorescent lamp to be miniaturized and to be made as compact as possible.
As one example of such a fluorescent lamp, a bulb-type fluorescent lamp is well known. This fluorescent lamp has multiples of U-shaped bulbs or straight bulbs that are set annularly on a holder. The neighboring bulbs are connected by bridge connection to form such an arc tube that provides a single serpentine discharge path inside the bulbs. The fluorescent lamp is so provided with the arc tube having the serpentine discharge path, the holder for holding the arc tube, and a base provided at the end of the holder.
Such a fluorescent lamp with a serpentine discharge path has a disadvantage that the horizontal light distribution of the lamp is likely to be nonuniform. As an example of technique for improving the horizontal light distribution, a bulb-type fluorescent lamp in which a rodlike reflector is provided in a space enclosed by multiples of U-shaped bulbs is proposed (such a bulb-type fluorescent lamp is hereinafter simply called xe2x80x9cfluorescent lampxe2x80x9d).
This conventional fluorescent lamp is explained below, with reference to FIGS. 1 and 2.
FIG. 1 illustrates a construction and manufacturing method of the fluorescent lamp. This fluorescent lamp has an arc tube 901 and a holder 902. A rodlike reflector 905 shown in FIG. 2 is placed on the holder 902, to improve the light distribution of the lamp.
The arc tube 901 is composed of three U-shaped bulbs 901a and a bridge connector 901b which connects neighboring U-shaped bulbs 901a. The arc tube 901 is fixed to the holder 902 so as to form a discharge path annularly.
To fix the reflector 905 to the holder 902, a stopper 905a is provided to the end of the reflector 905, and a stopper holding part 902a is provided to the holder 902. The stopper 905a has a notch with two legs.
A slit 905b formed between the two legs of the stopper 905a provides elasticity. This elasticity is exploited to insert the reflector 905 into the stopper holding part 902a from the side of the arc tube 901 (hereafter xe2x80x9carc tube sidexe2x80x9d), and engage the stopper 905a with the stopper holding part 902a. Hence the reflector 905 is fixed to the holder 902.
However, this type of fluorescent lamp has the following problems. First, some products still suffer from gradual deterioration of light distribution. Second, the productivity of this type of fluorescent lamp is not particularly good. More specifically, when setting the holder 902 to the arc tube 901, usually a silicon adhesive or the like is used to fix them together. Here, to keep the appearance of the lamp from being ruined by the excess adhesive which squeezes out of the contact area between the holder 902 and the arc tube 901, it is preferable to point upward the end of the arc tube 901 with electrode lead wires, and place the holder 902 onto the arc tube 901 from above. Meanwhile, when setting the reflector 905 to the holder 902, it is preferable to insert the reflector 905 in the direction designated by the arrow shown in FIG. 1, with the arc tube 901 and the holder 902 turned upside down. Thus, the arc tube 901 and the holder 902 have to be turned upside down during the manufacturing operation. This decreases the productivity of the fluorescent lamp.
In view of the above problems, the first object of the invention is to provide a fluorescent lamp with improved productivity and a manufacturing method for such a fluorescent lamp. The second object of the invention is to provide a fluorescent lamp which can maintain uniform light distribution for a long time.
The first object can be fulfilled by a fluorescent lamp including: an arc tube in which a serpentine discharge path is formed; a holder to which the arc tube is fixed at a predetermined position; and a light reflecting member which is fixed to the holder so as to have a predetermined positional relation with the arc tube, and reflects light emitted from the arc tube, wherein the light reflecting member has a reflecting part which reflects the light from the arc tube, and a fixing part which is fixed to the holder, the holder has a mounting part which includes an area that allows the reflecting part to pass through but does not allow the fixing part to pass through, and the light reflecting member is fixed to the holder by fixing the fixing part to the mounting part in a state where the reflecting part has been passed through the area.
This fluorescent lamp can be manufactured by a manufacturing method including: a holder fixing step for fixing a holder to an arc tube in which a serpentine discharge path is formed, the holder having an area that allows a reflecting part of a light reflecting member to pass through; and a light reflecting member setting step for setting the light reflecting member to the holder, by passing the reflecting part through the area from a side of the holder which is opposite to the arc tube, wherein the light reflecting member has a fixing part which cannot pass through the area, in addition to the reflecting part which can pass through the area, and the fixing part is fixed to the holder in a state where the reflecting part has been passed through the area.
With the above fluorescent lamp and manufacturing method, the process of turning the arc tube upside down becomes unnecessary, and the productivity is improved.
Also, the second object can be fulfilled by the fluorescent lamp of the above construction. The reason for this is given below.
After thorough study of the cause of degradation in light distribution of the conventional fluorescent lamp described above, the inventors of the present application found that part of the stopper 905a where the notch with two legs is present tends to become gradually deformed by heat generated during the illumination of the lamp. This deformation occurs in such a direction that makes the width of the slit 905b between the two legs smaller, and therefore brings about change in the engagement of the stopper 905a with the stopper holding part 902a. As a result, the position of the reflector 905 becomes unstable, which cause degradation in light distribution. According to the present invention, on the other hand, the diameter of the fixing part is likely to be larger than the diameter of the reflecting part. Accordingly, it is easy to prevent the occurrence of heat deformation between the reflector and the holder by taking measures such as the increase of the heat capacity of the fixing part, the divergence of heat generated during the illumination of the lamp, and the provision of a slit with one end closed, depending on the factors such as the shape of the fixing part. Hence the second object can be fulfilled.